Chemical source vessel with dip tube

ABSTRACT

A chemical vessel is disclosed comprising a dip tube and a level sensor tube arranged in an elongated counterbore incorporated into a housing of the chemical vessel. The chemical vessel may be configured to allow a pushback routine to take place, whereby a level of liquid in the chemical vessel is reduced to a point that the dip tube is free from liquid inside the dip tube or at the bottom of the dip tube. Once the dip tube is free of the liquid, then a vacuum source may be used to purge vapor within the chemical vessel without the risk of damage to the vacuum source.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Non-Provisional of, and claims priority to and thebenefit of, U.S. Provisional Patent Application No. 62/844,715, filedMay 7, 2019 and entitled “CHEMICAL SOURCE VESSEL WITH DIP TUBE,” whichis hereby incorporated by reference.

FIELD OF INVENTION

The present disclosure generally relates to an apparatus for processingsemiconductor wafers. More particularly, the disclosure relates to avessel in the apparatus for providing a vaporized gas precursor from aliquid source used for depositing a film on a semiconductor wafer in anatomic layer deposition (ALD) process, a chemical vapor deposition (CVD)process, or an epitaxial deposition process, for example.

BACKGROUND OF THE DISCLOSURE

In film deposition systems, gases are passed over semiconductor wafers,whereby the gases may react with other gaseous precursors in order toform a particular film. The gases may be produced from vaporizing liquidin a vessel.

The vessel may include a refill line to ensure that the vessel has asufficient amount of liquid source needed to provide a requisite amountof gaseous precursors. The vessel may be filled with an inlet valveattached to a dip tube. The vessel may also have an outlet valve throughwhich gas or liquid may exit the vessel. An example of such a vessel maybe disclosed in U.S. Pat. No. 6,077,356, entitled “Reagent Supply Vesselfor Chemical Vapor Deposition,” which is hereby incorporated byreference. The vessel may include a dip tube as well as a liquid levelsensor.

A chemical vessel 100 known in the art is illustrated in FIG. 1 . Thechemical vessel 100 comprises a vessel housing 110, a level sensor tube120, a plurality of level sensors 130A-130D, a dip tube 140, a valve150, and a gas or vacuum source 160. Within the vessel housing 110, anotch 170 is formed. The chemical vessel 100 may be used to store aliquid chemical that may later be vaporized into a gas for use in a filmdeposition process.

The plurality of level sensors 130A-130D may be located at particularspots along the level sensor tube 120 to indicate that a liquid insidethe vessel housing 110 is at a particular level. For example, a readingat level sensor 130A may indicate that the liquid inside the vesselhousing 110 is at a 75% level, a reading at level sensor 130B mayindicate that the liquid inside the vessel housing 110 is at a 65%level, a reading at level sensor 130C may indicate that the liquidinside the vessel housing 110 is at a 15% level, and a reading at levelsensor 130D may indicate that the liquid inside the vessel housing 110is at a 10% level.

Into the notch 170, the level sensor tube 120 may extend, but not thedip tube 140. Because the dip tube 140 does not extend into the notch170, this may result in a large amount of liquid in the vessel after thevacuum or gas source 160 pushes liquid down through the dip tube 140.

In addition, the refill line, which is the same line as the dip tube(along with other lines and tubes attached to the vessel), may undergoprocesses to remove liquid source through application of input gas andvacuum. When the vacuum is applied, it is desirable to ensure that thedip tube is free of any liquid both inside and below this tube, as thepresence of any liquid in the dip tube would result in liquid goingthrough the pump. The pump could then be damaged and create a safetyissue for operating personnel.

As a result, a vessel utilized for processing semiconductor wafers thatprevents liquid in the vessel from being drawn back through the dip tubeis desired. In addition, a method for verification that a liquid levelis below the dip tube is also desired.

SUMMARY OF THE DISCLOSURE

In accordance with one embodiment of the invention, a chemical vesselfor providing a chemical precursor for use in deposition ofsemiconductor films onto a substrate is disclosed. The chemical vesselcomprises: a vessel housing; a counterbore built into a bottom of thevessel housing; a level sensor tube extending from a top of the vesselhousing substantially into the counterbore, the level sensor tubecomprising a plurality of level sensors indicating a level of chemicalprecursor within the vessel housing; a dip tube extending from a top ofthe vessel housing to substantially a top of the counterbore; a vacuumsource coupled to the dip tube; and a vacuum valve connecting the vacuumsource to the dip tube; wherein the vacuum source is configured toremove a vapor of the chemical precursor from the vessel housing.

This summary is provided to introduce a selection of concepts in asimplified form. These concepts are described in further detail in thedetailed description of example embodiments of the disclosure below.This summary is not intended to identify key features or essentialfeatures of the claimed subject matter, nor is it intended to be used tolimit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

These and other features, aspects, and advantages of the inventiondisclosed herein are described below with reference to the drawings ofcertain embodiments, which are intended to illustrate and not to limitthe invention.

FIG. 1 is a cross-sectional illustration of a prior art chemical vessel.

FIG. 2 is a perspective illustration of a chemical vessel in accordancewith at least one embodiment of the invention.

FIGS. 3A-3C are cross-sectional illustrations of a chemical vessel inaccordance with at least one embodiment of the invention.

FIG. 4 is a top-down perspective illustration of a chemical vessel inaccordance with at least one embodiment of the invention.

FIG. 5 illustrates a method in accordance with at least one embodimentof the invention.

It will be appreciated that elements in the figures are illustrated forsimplicity and clarity and have not necessarily been drawn to scale. Forexample, the dimensions of some of the elements in the figures may beexaggerated relative to other elements to help improve understanding ofillustrated embodiments of the present disclosure.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Although certain embodiments and examples are disclosed below, it willbe understood by those in the art that the invention extends beyond thespecifically disclosed embodiments and/or uses of the invention andobvious modifications and equivalents thereof Thus, it is intended thatthe scope of the invention disclosed should not be limited by theparticular disclosed embodiments described below.

The illustrations presented herein are not meant to be actual views ofany particular material, structure, or device, but are merely idealizedrepresentations that are used to describe embodiments of the disclosure.

As used herein, the term “atomic layer deposition” (ALD) may refer to avapor deposition process in which deposition cycles, preferably aplurality of consecutive deposition cycles, are conducted in a processchamber. Typically, during each cycle the precursor is chemisorbed to adeposition surface (e.g., a substrate surface or a previously depositedunderlying surface such as material from a previous ALD cycle), forminga monolayer or sub-monolayer that does not readily react with additionalprecursor (i.e., a self-limiting reaction). Thereafter, if necessary, areactant (e.g., another precursor or reaction gas) may subsequently beintroduced into the process chamber for use in converting thechemisorbed precursor to the desired material on the deposition surface.Typically, this reactant is capable of further reaction with theprecursor. Further, purging steps may also be utilized during each cycleto remove excess precursor from the process chamber and/or remove excessreactant and/or reaction byproducts from the process chamber afterconversion of the chemisorbed precursor. Further, the term “atomic layerdeposition,” as used herein, is also meant to include processesdesignated by related terms such as, “chemical vapor atomic layerdeposition”, “atomic layer epitaxy” (ALE), molecular beam epitaxy (MBE),gas source MBE, or organometallic MBE, and chemical beam epitaxy whenperformed with alternating pulses of precursor composition(s), reactivegas, and purge (e.g., inert carrier) gas.

As used herein, the term “chemical vapor deposition” (CVD) may refer toany process wherein a substrate is exposed to one or more volatileprecursors, which may react and/or decompose on a substrate surface toproduce a desired deposition.

Chemical vessels may be used to hold a liquid precursor that is latervaporized when used to form a film. FIG. 2 illustrates a chemical vessel200 in accordance with at least one embodiment of the invention. Thechemical vessel 200 comprises a vessel housing 210, a first valve 220A,a second valve 220B, a third valve 220C, and a level sensor tube port230.

The first valve 220A may be connected to a gas source (not illustrated).The second valve 220B may be connected to a vacuum source or a liquidsource (not illustrated). The third valve 220C may be connected to areaction chamber (not illustrated), where deposition of a film may takeplace. Each of first valve 220A, second valve 220B, and/or third valve220C may comprise a manual or pneumatic valve. The level sensor tubeport 230 may allow for electrical connections to a controller, to aprocessor, or to a heating element (not illustrated).

The chemical vessel 200 may include additional parts illustrated in FIG.3A. The chemical vessel 200 may also include a dip tube 240, a levelsensor tube 250, a plurality of level sensors 260A-260D, and acounterbore 270. The dip tube 240 may be attached to the second valve220B. The level sensor tube 250 may be connected to the level sensortube port 230. The counterbore 270 may be a notch formed within a bottomof the vessel housing 210. The level sensor tube 250 may extendsubstantially into the counterbore 270, while the dip tube 240 mayextend to approximately the top of the counterbore 270.

The plurality of level sensors 260A-260D may be located at particularspots along the level sensor tube 250 to indicate that a liquid insidethe vessel housing 210 is at a particular level. For example, a readingat level sensor 260A may indicate that the liquid inside the vesselhousing 210 is at a 75% level, a reading at level sensor 260B mayindicate that the liquid inside the vessel housing 210 is at a 65%level, a reading at level sensor 260C may indicate that the liquidinside the vessel housing 210 is at a 5% level, and a reading at levelsensor 260D may indicate that the liquid inside the vessel housing 210is at a 1% level.

The chemical vessel 200 may operate in a situation illustrated in FIG.3B. The counterbore 270 may be filled with a safe amount of liquidprecursor 280A and an excess amount of liquid precursor 280B. The excessamount of liquid precursor 280B has the potential to be sucked up withinthe dip tube 240 as the second valve 220B may be connected to a vacuumsource. The vacuum source may be connected to a pump, which may beadversely affected by the excess amount of liquid precursor 280B.

As a result, the excess amount of liquid precursor 280B may be removedthrough a process of operating the first valve 220A and the third valve220C. The safe amount of liquid precursor 280A may be reflected as theamount that would reach the level sensor as reflected in FIG. 3C. Oncethe level of liquid precursor in the vessel is at the safe amount 280A,a vacuum source may be operatively connected to the second valve 220Band the dip tube 240 safely without any of the liquid precursor going upthe dip tube 240.

FIG. 4 illustrates a shape of the counterbore 270 within the vesselhousing 210. The counterbore 270 may be shaped in other ways, such as anellipse, a circle, or a rectangle, for example. One of ordinary skill inthe art may employ any shape for the counterbore 270 so long as the areaencompasses both the area under the dip tube 240 and the level sensortube 250.

The chemical vessel 200 may be operated in different ways. The chemicalvessel 200 may be refilled during a process and also may be emptied aswell. A process 300 for operating the chemical vessel 200 is illustratedin FIG. 5 in accordance with at least one embodiment of the invention.Operating the process 300 may not only ensure that liquid cannot bedrawn back through the dip tube 240, but also allow for a purge routineto be run in the chemical vessel 200 in allowing for safe removal of thechemical vessel 200 during maintenance.

The process 300 results in removal of a liquid precursor in the vesselhousing 210 to a remote located liquid source. The process 300 maycomprise an initiate pushback step 310, a reduce liquid to the first lowsensor step 320, a reduce liquid to the bottom of the dip tube step 330,and a purge vapor step 340. During the initiate pushback step 310,liquid precursor in the vessel housing 210 may exit the dip tube 240.The reduce liquid to the first low sensor step 320 may result in thelevel of liquid precursor being at the level sensor 260C. The reduceliquid to the bottom of the dip tube 330 may result in the level ofliquid precursor being at the level sensor 260D.

At this point, the level of liquid precursor may be at the safe amount280A. The second valve 220B may be opened and a vacuum may be employedto remove vapor within the chemical vessel 200.

The particular implementations shown and described are illustrative ofthe invention and its best mode and are not intended to otherwise limitthe scope of the aspects and implementations in any way. Indeed, for thesake of brevity, conventional manufacturing, connection, preparation,and other functional aspects of the system may not be described indetail. Furthermore, the connecting lines shown in the various figuresare intended to represent exemplary functional relationships and/orphysical couplings between the various elements. Many alternative oradditional functional relationship or physical connections may bepresent in the practical system, and/or may be absent in someembodiments.

It is to be understood that the configurations and/or approachesdescribed herein are exemplary in nature, and that these specificembodiments or examples are not to be considered in a limiting sense,because numerous variations are possible. The specific routines ormethods described herein may represent one or more of any number ofprocessing strategies. Thus, the various acts illustrated may beperformed in the sequence illustrated, in other sequences, or omitted insome cases.

The subject matter of the present disclosure includes all novel andnonobvious combinations and subcombinations of the various processes,systems, and configurations, and other features, functions, acts, and/orproperties disclosed herein, as well as any and all equivalents thereof.

The invention claimed is:
 1. A chemical vessel for providing a chemicalprecursor for use in deposition of semiconductor films onto a substrate,the chemical vessel comprising: a vessel housing; a counterbore builtinto a bottom of the vessel housing; wherein the counterbore comprises:a first end with a first diameter and a second end with a seconddiameter, wherein the first diameter is greater than the seconddiameter; and a continually tapering wall from the first end to thesecond end, a level sensor tube extending from a top of the vesselhousing into the counterbore, the level sensor tube comprising aplurality of level sensors indicating a level of chemical precursorwithin the vessel housing; a dip tube extending from a top of the vesselhousing to approximately a top of the counterbore; a vacuum sourcecoupled to the dip tube; and a vacuum valve connecting the vacuum sourceto the dip tube; wherein the vacuum source is configured to remove avapor of the chemical precursor from the vessel housing; and wherein alength of the level sensor tube within the vessel housing is greaterthan a length of the dip tube within the vessel housing.
 2. The chemicalvessel of claim 1, wherein the counterbore is shaped in at least one of:rectangular, circular, or elliptical.
 3. The chemical vessel of claim 1,wherein the plurality of level sensors are disposed at differentlocations on the level sensor tube.
 4. The chemical vessel of claim 1,further comprising a reaction chamber valve configured to send avaporized chemical precursor to a reaction chamber.
 5. The chemicalvessel of claim 1, further comprising an inlet valve coupled to a gassource.
 6. The chemical vessel of claim 1, further comprising a levelsensor port to which the level sensor tube is coupled.
 7. A method ofoperating the chemical vessel of claim 1, the method comprising:initiating a push back of the chemical precursor to an external liquidchemical precursor source; reducing a level of the chemical precursor toa first level sensor; reducing a level of the chemical precursor tobelow the dip tube; and purging a vapor of the chemical precursor to thevacuum source.
 8. A reaction system for depositing a semiconductor filmonto a substrate, the reaction system comprising: the chemical vessel ofclaim 1; a reaction chamber; and a substrate holder configured to holdat least one substrate.